If you're playing with ice, remember that ice can break with very sharp edges.  Run your ice under warm water to round off edges before you insert it anywhere, and don't use fragile ice structures that may break inside sensitive body parts.

Zinc promotes healing.   Taking Zinc after heavy play can help bruises and cuts heal more quickly.

Use only paraffin candles for wax play.   Colored wax burns hotter.  Candles held closer than 6 inches to the body can cause serious burns.

To check that any rope bondage is not likely to be too tight, you should be able to pass one finger between the rope and the skin. If you cannot, then the Bottom may have circulation problems. If there is room for two or more fingers, the Bottom may be able to get free. A little practice is all you will need to the tension right.

Wrapping is the uncomfortable effect caused by the tails of the flogger landing too high, and wrapping over the shoulder. This can be avoided when it happens by stepping back (so the tails CANNOT reach that far) and/or lowering one's stance into a deeper crouch

Learn, practice,  and perfect.